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United States Patent |
5,172,749
|
Flemming
|
December 22, 1992
|
Continuous steel casting mold
Abstract
A continuous steel casting mold includes walls with base members of copper
alloy which are provided with cooling ducts. In order to improve the wear
resistance and to prevent cracks, a working coating of pure copper is
provided on the base members. It is also possible to provide an
intermediate layer of pure copper on the base member and a working coating
on the intermediate layer. The layer of pure copper has a thickness of at
least 0.2 mm.
Inventors:
|
Flemming; Gunter (Erkrath, DE)
|
Assignee:
|
SMS Schloemann Siemag Aktiengesellschaft (Dusseldorf, DE)
|
Appl. No.:
|
812440 |
Filed:
|
December 23, 1991 |
Foreign Application Priority Data
Current U.S. Class: |
164/418; 164/138; 164/459 |
Intern'l Class: |
B22D 011/00; B22C 003/00 |
Field of Search: |
164/418,138,459
|
References Cited
U.S. Patent Documents
4023612 | May., 1977 | Jackson | 164/459.
|
4635702 | Jan., 1987 | Kolakowski et al. | 164/418.
|
Foreign Patent Documents |
56-68555 | Jun., 1981 | JP | 164/418.
|
60-18252 | Jan., 1985 | JP | 164/418.
|
2-220736 | Sep., 1990 | JP | 164/459.
|
Primary Examiner: Seidel; Richard K.
Assistant Examiner: Knapp; Jeffrey T.
Attorney, Agent or Firm: Anderson Kill Olick & Oshinsky
Claims
I claim:
1. A continuous steel casting mold for continuously casting thin slabs, the
mold comprising broad side walls and narrow side walls between the broad
side walls, the broad side walls defining a widened pouring zone, the
broad side walls comprising a base member of copper alloy, the base member
having cooling ducts, each broad side wall having a surface facing the
pouring zone, the base member having on the surface thereof a working
coating, the working coating being a layer of pure copper having a
thickness of at least 0.2 mm.
2. The continuous steel casting mold according to claim 1, wherein the pure
copper layer has a thickness of 1-8 mm.
3. A continuous steel casting mold for continuously casting thin slabs, the
mold comprising broad side walls and narrow side walls between the broad
side walls, the broad side walls defining a widened pouring zone, the
broad side walls comprising a base member of copper alloy, the base member
having cooling ducts, each broad side wall having a surface facing the
pouring zone, the base member having on the surface thereof an
intermediate layer, the intermediate layer being a layer of pure copper
having a thickness of at least 0.2 mm and a working coating being placed
on the intermediate layer.
4. The continuous steel casting mold according to claim 3, wherein the
intermediate layer has a thickness of 0.2-0.4 mm.
5. The continuous steel casting mold according to claim 3, wherein the
working coating consists essentially of nickel.
6. The continuous steel casting mold according to claim 3, wherein the
working coating consists essentially of chromium.
7. The continuous steel casting mold according to claim 3, wherein the
working coating consists essentially of molybdenum.
8. The continuous steel casting mold according to claim 3, wherein the
working coating consists essentially of metal ceramics.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a continuous steel casting mold whose
walls are composed of a base member of copper alloy provided with cooling
ducts and of a working coating provided on the base member.
2. Description of the Related Art
The most important requirements made of continuous steel casting molds are
good heat conductivity, resistance to wear and dimensional stability. In
order to meet these requirements, continuous steel casting molds have been
developed which have shaping walls of pure copper, copper alloy and of
copper coated with chromium and nickel.
EP-A-0 383 934 discloses continuous steel casting molds whose walls which
consist of copper or copper alloy have on the working side a coating of
nickel alloy. In order to flatten the differences in degrees of hardness
between the copper wall and the very hard nickel alloy layer and for
improving the connection, an intermediate layer of nickel is arranged
between the copper wall and the layer of nickel alloy.
In continuous casting plants for casting steel strips developed more
recently, the molds used in the plants are subjected to significantly more
problems due to wear, stress-related distortion and the formation of
cracks. This is because the casting rates are higher and the mold cavities
have a complex shape.
The invention starts from the finding that local high stress peaks at the
surface lead to damage, particularly to the formation of cracks, because
of the fact that expansion is prevented. The tendency to form cracks and
the spreading of cracks is increased by the formation of brass which is
due to diffusion of zinc into the working surface.
SUMMARY OF THE INVENTION
Therefore, it is the object of the present invention to provide a
continuous steel casting mold with broad side walls which form an upper
widened portion, wherein the mold walls have even under increased loads an
improved resistance to wear and an increased service life and particularly
an excellent resistance to cracks and dimensional stability.
In accordance with the present invention, in a mold for continuously
casting thin slabs, whose broad side walls form a widened pouring zone,
the base members are provided with a layer of pure copper having a
thickness of at least 0.2 mm.
Because of the high heat conductivity, the intermediate layer of pure
copper according to the present invention results in a quick heat removal
and, thus, in a reduction of the surface temperature. The toughness of the
pure copper prevents or reduces the spreading of cracks, so that damage to
the strain-hardened base member of copper alloy is prevented. This result
cannot be obtained when using the known intermediate layers which are
applied by nickel-plating and have a thickness of less than 10 .mu.m.
The pure copper layer may form a working layer on the base member and may
have a thickness of 1-8 mm. The toughness of this material prevents the
formation of cracks and the spreading of cracks. The continuous wear
prevents the formation of brass.
In accordance with a particularly advantageous feature of the invention,
the pure copper layer forms a layer underneath a wear-resistant working
coating, wherein the pure copper layer acts as a barrier and has a
thickness of 0.2-0.4 mm.
The working coating applied on the intermediate layer may be of nickel,
chromium, molybdenum or alloys thereof or of metal ceramics. The
intermediate layer and the working layer may be applied in the known
manner either electrolytically or by spraying.
The various features of novelty which characterize the invention are
pointed out with particularity in the claims annexed to and forming a part
of this disclosure For a better understanding of the invention, its
operating advantages attained by its use, reference should be had to the
drawing and descriptive matter in which there are illustrated and
described preferred embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWING
In the drawing:
FIG. 1 is a schematic top view of a continuous steel casting mold with
widened pouring zone;
FIG. 2 is a vertical sectional view of the continuous steel casting mold
taken along sectional line II--II of FIG. 1;
FIG. 3 is a partial sectional view, on a larger scale, of the upper side of
the mold wall; and
FIG. 4 is a view similar to FIG. 3, showing a different type of coating.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As illustrated in FIGS. 1 and 2, a continuous steel casting mold includes
two broad side walls 1, 2 and two narrow side walls 3, 4 arranged between
the broad side walls 1, 2. The broad side walls 1, 2 form a widened
pouring zone 6 for receiving a pouring tube 5. The pouring zone 6 extends
over a portion of the mold height. The mold wall includes a base member 8
which is provided with cooling ducts 7.
In the embodiment illustrated in FIG. 3, the base member 8 is provided with
a working coating 9 of pure copper.
In the second embodiment shown in FIG. 4, the base member 8 is provided
with an intermediate layer 10 of pure copper which is arranged underneath
a working coating 11. In this case, the working coating 11 advantageously
is of nickel or metal ceramics.
Both embodiments effectively prevent the formation of cracks and the
increase of cracks in the base member 8.
While specific embodiments of the invention have been shown and described
in detail to illustrate the inventive principles, it will be understood
that the invention may be embodied otherwise without departing from such
principles.
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